If you consistently have a bunch of tabs open when using Firefox, one problem you may have is following the ‘breadcrumb’ of how tabs relate to each other. For example, if you are looking at search results on troubleshooting and then follow a link which opens a new tab and follow another link which opens another new tab (etc., etc.), the tabs can be cumbersome to backtrack. To help with this, check out the Tree Style Tab add-on:

This provides tree-style tab bar, like a folder tree of Windows Explorer. New tabs opened from links (or etc.) are automatically attached to the current tab. If you often use many many tabs, it will help your web browsing because you can understand relations of tabs.

Their explanation hopefully clarifies my example, but checkout the screenshots on the link and you will see exactly what it does.

I find this particularly useful when researching code documentation because I can jump back and forth between my search results and any message boards and articles I opened from there.